Building panels provided with a mechanical locking system comprising a displaceable and resilient tongue cooperating with a tongue groove for vertical locking is known and disclosed in, e.g., WO2006/043893 and WO2007/015669, The tongue is a separate part and is made of, e.g., plastic and inserted in a displacement groove at an edge of a panel. The tongue is pushed into the displacement groove during a vertical assembling of the panels and springs back into the tongue groove of an adjacent panel when the panels have reached a locked position.
Also known is a locking system for panels comprising a tongue, which is displaceable along the edge of a panel, see e.g. WO2009/116926, and cooperates with a tongue groove for vertical locking. The tongue is a separate part and is provided with several protrusions, which initially match recesses of the tongue groove. The panels may be assembled by a vertical movement and the tongue is displaced to a position in which the protrusions no longer match the recesses in order to obtain the vertical locking.
Further known is a locking system comprising a tongue provided with, e.g., a wedge element. Two adjacent panels edges are locked by displacing the tongue along the adjacent edges, see, e.g., WO2008/004960.
Although the description relates to floor panel, the description of techniques and problems thereof is applicable also for other applications, such as panels for other purposes, for example, wall panels, ceiling panels, furniture etc.
A drawback with the known systems is that a locking system comprising a displaceable tongue requires a rather thick panel to ensure that the locking system meets the strength requirement.
The above description of various known aspects is the applicant's characterization of such, and is not an admission that any of the above description is considered as prior art.